Stable Carbon Isotope Signature of Methane Released From Phytoplankton

Unidad de excelencia María de Maeztu CEX2019-000940-MAquatic ecosystems play an important role in global methane cycling and many field studies have reported methane supersaturation in the oxic surface mixed layer (SML) of the ocean and in the epilimnion of lakes. The origin of methane formed under oxic condition is hotly debated and several pathways have recently been offered to explain the "methane paradox." In this context, stable isotope measurements have been applied to constrain methane sources in supersaturated oxygenated waters. Here we present stable carbon isotope signatures for six widespread marine phytoplankton species, three haptophyte algae and three cyanobacteria, incubated under laboratory conditions. The observed isotopic patterns implicate that methane formed by phytoplankton might be clearly distinguished from methane produced by methanogenic archaea. Comparing results from phytoplankton experiments with isotopic data from field measurements, suggests that algal and cyanobacterial populations may contribute substantially to methane formationobserved in the SML of oceans and lakes

A fast and sensitive method for the continuous in situ determination of dissolved methane and its d13C-isotope ratio in surface waters

A fast and sensitive method for the continuous determination of methane (CH4) and its stable carbon isotopic values (d13C-CH4) in surface waters was developed by applying a vacuum to a gas/liquid exchange membrane and measuring the extracted gases by a portable cavity ring-down spectroscopy analyser (M-CRDS). The M-CRDS was calibrated and characterized for CH4 concentration and d13C-CH4 with synthetic water standards. The detection limit of the M-CRDS for the simultaneous determination of CH4 and d13CCH4 is 3.6 nmol L21 CH4. A measurement precision of CH4 concentrations and d13C-CH4 in the range of 1.1%, respectively, 1.7& (1r) and accuracy (1.3%, respectively, 0.8& [1r]) was achieved for single measurements and averaging times of 10 min. The response time s of 5765 s allow determination of d13C-CH4 values more than twice as fast than other methods. The demonstrated M-CRDS method was applied and tested for Lake Stechlin (Germany) and compared with the headspace-gas chromatography and fast membrane CH4 concentration methods. Maximum CH4 concentrations (577 nmol L21) and lightest d13C-CH4 (235.2&) were found around the thermocline in depth profile measurements. The M-CRDS-method was in good agreement with other methods. Temporal variations in CH4 concentration and d13C-CH4 obtained in 24 h measurements indicate either local methane production/oxidation or physical variations in the thermocline. Therefore, these results illustrate the need of fast and sensitive analyses to achieve a better understanding of different mechanisms and pathways of CH4 formation in aquatic environments

P450-mediated dehydrotyrosine formation during WS9326 biosynthesis proceeds via dehydrogenation of a specific acylated dipeptide substrate

WS9326A is a peptide antibiotic containing a highly unusual N-methyl-E-2-3-dehydrotyrosine (NMet-Dht) residue that is incorporated during peptide assembly on a non-ribosomal peptide synthetase (NRPS). The cytochrome P450 encoded by sas16 (P450Sas) has been shown to be essential for the formation of the alkene moiety in NMet-Dht, but the timing and mechanism of the P450Sas-mediated α,β-dehydrogenation of Dht remained unclear. Here, we show that the substrate of P450Sas is the NRPS-associated peptidyl carrier protein (PCP)-bound dipeptide intermediate (Z)-2-pent-1′-enyl-cinnamoyl-Thr-N-Me-Tyr. We demonstrate that P450Sas-mediated incorporation of the double bond follows N-methylation of the Tyr by the N-methyl transferase domain found within the NRPS, and further that P450Sas appears to be specific for substrates containing the (Z)-2-pent-1′-enyl-cinnamoyl group. A crystal structure of P450Sas reveals differences between P450Sas and other P450s involved in the modification of NRPS-associated substrates, including the substitution of the canonical active site alcohol residue with a phenylalanine (F250), which in turn is critical to P450Sas activity and WS9326A biosynthesis. Together, our results suggest that P450Sas catalyses the direct dehydrogenation of the NRPS-bound dipeptide substrate, thus expanding the repertoire of P450 enzymes that can be used to produce biologically active peptides

Minimum Information about a Biosynthetic Gene cluster

A wide variety of enzymatic pathways that produce specialized metabolites in bacteria, fungi and plants are known to be encoded in biosynthetic gene clusters. Information about these clusters, pathways and metabolites is currently dispersed throughout the literature, making it difficult to exploit. To facilitate consistent and systematic deposition and retrieval of data on biosynthetic gene clusters, we propose the Minimum Information about a Biosynthetic Gene cluster (MIBiG) data standard.Chemistry and Chemical Biolog

“Onomastic Archaeology” (with Reference to German Toponymy)

Автор статьи исходит из того, что археология и историческая лингвистика, используя каждая свои методы, преследуют одну и ту же цель — понять и интерпретировать культуру доисторического и раннего исторического периодов; как следствие, эти науки могут успешно дополнять и обогащать друг друга. Предлагая назвать область пересечения археологии и лингвистики «лингвистической археологией», автор видит современные возможности этой дисциплины не столько в исследовании нарицательной лексики, сколько в исследовании тех имен собственных, которые дошли до нас с древнейших времен: тем самым, наряду с широким понятием «лингвистическая археология», в статье вводится более узкое понятие «ономастическая археология». В плане взаимодействия исторической ономастики и собственно археологической науки автору представляется наиболее перспективным изучение топонимов, поскольку во многих случаях они имеют давнюю историко-географическую атрибуцию и остаются связанными с определенным местом или пространством на протяжении длительного времени. В качестве иллюстрации в статье приводится несколько названий из топонимикона Южной Германии, для которых на основе этимологического анализа устанавливается древнекельтское происхождение. Поскольку соответствующие топонимы, согласно результатам анализа, обозначали не что иное, как укрепленные поселения древних кельтов, полученные лингвистические данные в перспективе могут служить ценным ориентиром для археологических поисков и, далее, для реконструкции древнекельтской культуры. По мнению автора, помимо ойконимов, важнейшую роль в ономастической археологии играют гидронимы, в которых, благодаря общеязыковым механизмам метонимии, могут сохраняться имена раннеисторических археологических памятников, упоминаемые в древних источниках, но ныне утраченные. Именно гидронимы, как показано автором, являются и наиболее показательной основой для выявления «языкового ландшафта» той или иной археологической культуры. В статье это иллюстрируется на примере засвидетельствованной в Германии ясторфской культуры, в ареале которой преобладают германские гидронимы, хотя встречаются и названия иного происхождения. В заключительном разделе статьи доминирование «германской» языковой составляющей в границах ясторфской культуры показано также на примере этнонима вагры, относящегося к славянской этнической группе. Этот этноним, по мнению автора, был либо перенят в период двуязычия славянской группой у предшествующего германского населения, либо возник в результате «внешнего» присвоения безымянному славянскому племени уже существующего германского названия.The author argues that archaeology and historical linguistics, each using their own tools, both seek to understand and interpret cultures of the prehistoric and early historical periods and, thus, can enrich and supplement each other. The author believes that the most potential of what he proposes to call “linguistic archaeology” is concentrated primarily in the study of proper names, which makes it possible to complement the general notion of “linguistic archaeology” with a narrower term — “onomastic archaeology”. This interdisciplinary cooperation can be most fruitful in the field of the study of place names, since the latter generally have a reliable historical and geographical attribution and are linked with a particular place or area during a relatively long period of time. The suggested approach is illustrated by some Southern German place names of Celtic origin. The etymological analysis shows that they all served to designate Celtic fortified settlements which makes these onomastic data valuable for further archaeological investigations and reconstruction of ancient Celtic culture. The author suggests that, besides oikonyms, hydronyms also play a significant role because of their capacity to conserve, due to metonymic transfer, the names of early historical monuments mentioned in ancient sources but considered to be lost. Referring to the Jastorf culture, whose area of diffusion displays, alongside with prevailing Germanic hydronyms, names of other origin, the author shows that hydronyms can be particularly important when reconstructing the “linguistic landscape” of an archaeological culture. In the concluding section of the article the prevalence of the Germanic linguistic component within the Jastorf culture area is illustrated by the analysis of the name of the ancient Slavic tribe of Wagri. In the author’s opinion, this ethnonym was either borrowed from an earlier Germanic population of that area during the period of bilingualism or adopted by the unnamed Slavic tribe as an already existing Germanic name.Редколлегия журнала выражает благодарность за помощь в подготовке статьи к публикации К. Хенгсту и В. В. Алпатову